1. Field of Art
This invention relates to sealed containers and to a method of sealing a glass container by induction heating a foil membrane and adhesive resin thereon to seal the membrane to a raised bead on the mouth of the container.
2. Brief Description of the Prior Art
Induction heat sealing of metal foil membranes on plastic containers is well known as for example is disclosed in U.S. Pat. Nos. 2,937,481; 3,632,004; 3,767,076 and 3,815,314, among others. The metal foil membrane typically has a heat seal resin of thermoplastic material thereon which is sealed to the plastic container under heat and pressure. Pressure applied against the top of an overcap presses the foil membrane against a sealing surface on the container to form a continuous seal around the container mouth. Plastic containers are sufficiently flexible to compensate for irregularities in the sealing surfaces and non-parallelism between the sealing surface and the base of the container. Melting the plastic in the container to fuse it to the diaphragm as in U.S. Pat. Nos. 2,937,481 and 3,632,004 also increases the area of contact under pressure to further compensate for irregularities in the sealing surface on plastic containers.
It is also known to induction heat seal metal foil membranes on glass containers as is for example disclosed in United States Adcock et al U.S. Pat. No. 3,460,310. However, glass containers typically have irregularities in their dimensions which make it difficult to get a continuous seal around a container mouth. Localized dips on the sealing surface of wide mouth glass containers and non-parallelism between the top surface and the base of the glass containers have prevented the adoption of low-cost closure systems on glass containers. A prime example of a low-cost closure system is a plastic snap cap with a coated or laminated foil/adhesive liner or membrane which can be hermetically sealed to the mouth of a container with known high speed induction heat sealing techniques.
It is also known to provide a small upwardly projecting bead on a bottle mouth to improve sealing characteristics as is disclosed in U.S. Pat. Nos. 1,077,538; 2,109,805; 2,403,511 and 2,620,938.
A system is desired for high speed induction heat sealing of glass containers using low-cost closures.